For hydraulic control mechanisms, electrorheological fluid valves have been developed. A typical electrorheological fluid valve includes two spaced electrodes forming a fluid channel. An electric potential between the electrodes causes an electric field in the flow channel increasing the viscosity of the electrorheological fluid valve therein.
The uniformity and repeatability of the electrode gap is important. For robotic applications, small size, inexpensive valves are needed. In U.S. Pat. No. 5,099,884, incorporated herein by this reference, “channel plates” alternate with printed circuit board “electrode plates” clamped together using tie rods.
Yoshida et al. “Fabrication of Microelectrode-Rheological Valves (ER valves) by Micromachining and Experiments”, Sensor and Actuators A 95 (2002) 227-233, also incorporated herein by this reference, proposes a “microvalve” fabricated by micromachining techniques.